Costumed
by Cora Clavia
Summary: And then she gets to infiltrate a strip club and Castle is positive that he is currently in a very special type of paradise that he in no way deserves. Season 5. Oneshot. Kind of pwpish. Sorry.


The day she has to help solve a case by posing as a librarian really might be the greatest day of his life.

He _really_ thinks he's hit the jackpot when Kate walks into the bullpen in her "librarian" outfit. The blouse and sweater are nothing new. The pencil skirt is. It's just snug enough to tease, but long enough to say _don't touch_. The tech guy gave her fake glasses equipped with a camera. Her hair is twisted back into a knot.

He doesn't think he's ever seen anything so sexy.

At the library, it's disappointingly tame. She doesn't have much to do. She just re-shelves books, occasionally glancing around; it's ostensibly to see if people are getting rambunctious, but really she's scanning the room for a suspect. Castle eyes her covetously from behind the Julius Caesar biography he snagged on his way in. He looks around. He's not the only one watching her. A lanky teenage kid at a table nearby is staring, slack-jawed. Apparently today's the day he discovers women.

Kate finally gets eyes on their suspect and murmurs into her hidden microphone, and uniforms swarm in quickly and remove the guy quick, quiet, without much trouble. Mission accomplished. Well done.

She grabs a couple books and heads for the stairs, shooting Castle a look that says _Now._

And in spite of her myriad previous stern commands that they are _professional_ and no touching or kissing or looking or _thinking_ outside their respective bedrooms (and kitchens and living rooms and offices and pantries and showers), minutes later they're locked in a dark closet in the back of the basement, tucked back among shelves of dusty old volumes. Her skirt is around her waist and he claps his hand over her mouth to muffle her moaning as he thrusts into her, growling. She comes hard, biting his hand as her fingers clench the shelf of Russian literature behind her.

She makes him leave the closet before she does. He manages to steal one last, long kiss before she shoves him out. It takes him a long time to stop grinning, even after she re-appears upstairs, cleaned up and tidy and looking like she absolutely did not just have sex with him in a dark closet.

That night she walks into his bedroom in her librarian outfit and says _You know what the penalty is for an overdue book, Mr. Castle?_

He gives it to her. With interest.

* * *

She acts furious the first time she has to wear a turtleneck to work because of him.

She's not. He can tell she's not. She certainly wasn't complaining when he gave it to her. She was too busy clutching at his shoulders and whimpering while he pushed her back against the wall of her shower and her hips rolled against his. But the ripe red-purple mark under her left ear now is too dark to go unnoticed, too vivid even to be hidden under makeup. She had to do that last week.

He can't help but laugh when he points it out to her while she's getting dressed in the morning. She throws off her half-buttoned shirt and digs into her drawer, grumbling something that sounds like _uncontrollable manchild_ as she roots around, looking for a shirt with a higher collar. He doesn't help. He's never really helpful when she's trying to put clothes on.

They get to work separately. They're still keeping it secret. He hands her coffee and a napkin, which she unfolds to find that he's written _Sorry_ in small letters next to a smiley face_. _

It's when she shoots him a mild, unconvincing attempt at a glare that he realizes she's in costume again.

Today she's dressed as _not_ his lover.

And the thing he loves most is that it really is a costume now.

* * *

And then she gets to infiltrate a strip club and Castle is positive that he is currently in a very special type of paradise that he in no way deserves.

She borrows clothes from Vice and stalks into the ladies' room with an armful of what looks like delightfully skimpy garb. He's not disappointed. She steps back out into the bullpen and everyone stares. Everyone. Even happily married Kevin Ryan just gapes.

For his part, Castle gulps, shifting uncomfortably in his chair, trying not to give away the fact that this tall, smoky-eyed wet dream in the sluttiest little schoolgirl costume he's ever seen is _his_. She's all his. Stilettos and endlessly long legs and a skirt that doesn't quite cover her red panties and a flimsy excuse for a shirt that doesn't come close to covering her lacy red bra. And her hair. Sex hair. It really is sex hair, because he has seen her hair after sex now and this is _exactly_ what it looks like after he's run his hands through it and she's writhed around on his pillows.

_Fuck_.

She stops at her desk and flicks a quick glance around the room. "Oh, cool it, guys. I'm not actually taking any of it off."

...still hot.

At the club, Castle's in agony. She's flirting hard, trying desperately to catch their guy's attention, and it ends up being her all but giving the bastard a lapdance, teasing him with those _come on and fuck me_ looks that she _knows_ she has. Castle grits his teeth and clenches his fists, sitting across the room with Ryan and Esposito, because Kate is driving him insane right now but he can't touch her.

But they get nowhere - apparently this is the wrong guy - and Kate sends him back to the loft while she finishes up stripper duty and checks in at the precinct. He's scowling out the window of the cab as it pulls up to his building when he gets the text message. It's six words long.

Shit, shit she cannot just _say_ things like that. Not when she just spent forty minutes making him so hard he's uncomfortable.

By the time Kate finally gets to his place - he thanks everything in the world his mother is out for the evening - he's pissed off and turned on, and she barely gets inside the door before he pushes her up against it. It's not until he finally pulls back for air that he realizes she hasn't changed clothes. He tugs her coat off her shoulders to find her still in her stripper outfit. Fuck fuck _fuck_.

He all but drags her back to his bedroom in this hot angry desperate tangle, where she's trying to pull his shirt off and he's trying to get his hand up her skirt and they're both kind of succeeding. Her breath is coming out in sharp little puffs of air, her eyes wide, and her pupils are so dilated he can't stop himself because he knows she likes it when he gets rough.

He doesn't even undress her, just pushes her underwear aside and growls _turn around_ into her ear. She obeys. He slides his hand between her legs, trails over her with one finger and she's already so wet, her breasts rising and falling rapidly under the soft red lace and white cotton, her hands gripping her headboard desperately. He tugs her skirt up, pulling her hips into his, and she lets out a long moan as he slides into her.

He's already so close he's not going to last, he knows, especially with her trembling, her thighs taut under his fingertips. He buries his face in her hair, inhaling deeply as he pushes inside her, She's keening, choked noises spilling from her parted lips as she arches into him helplessly, her inner muscles tightening around him and _fuck_, Kate, come on, come on -

He bites her neck and slides his thumb over her clit and thrusts _hard_ and just _fuck_. She clenches around him with a high-pitched, shuddering cry and he follows, his hips bucking hard as he spills into her in hot spurts, jerky and messy and so utterly spent he can't move.

When he finally comes to, she's slumped on the mattress beside him, breathing hard. Her face is flushed, a lovely pink peppered down her throat, over her collarbone, and her lips are red and swollen. She's so gorgeous it almost hurts to look at her.

He swallows. "That was, uh. Intense."

"Yeah." She runs a lazy hand over his forearm. "You were jealous, weren't you?"

"Yeah," he mumbles, eyes closed. It's stupid, he's an idiot, he's a caveman, but he can't help it.

"Yeah, I could tell." He feels the soft, light feather of her mouth as she presses a kiss to his shoulder. Her lips are curved against his sweaty skin. She's smiling. "You don't want me to be a stripper?"

"I don't like you trying to seduce other guys." And if that makes him petty, well, he really doesn't care.

"What if I needed the money? Cops aren't rich, you know." She pokes him in the arm. "I could just strip on weekends."

"No. No stripping. Except for me," he grumbles.

"You trying to make me a kept woman, Castle?"

"As long as I get to keep you."

It's out of his mouth before he realizes how it sounds, and he holds his breath. It's a long second before she speaks.

"I can live with that."

He finally looks over to find her smiling at him, her eyes shining and warm with unspoken things and really, it makes no sense, but somehow, immediately after rough, semi-angry sex with her dressed as a slutty schoolgirl, he's pretty sure they just tacitly agreed that she's more or less in love with him.

* * *

By Halloween, the boys have figured it out. They're smart. They're observant. They also caught the two of them that one time when Castle's hand was up her shirt and she was straddling his thigh and biting his earlobe because his office in the Old Haunt was supposed to be _locked_, come _on_.

But he throws a great Halloween party and invites everyone. Pulls out all the stops, decorates the loft, puts out plenty of food and a fantastic bar. It's a smash. Even Gates shows up and seems to enjoy herself.

He ends up dressing as Han Solo. He's always wanted to. And he looks damn good, if he says so himself. Kate walks into his loft dressed as a Ghostbuster. Ryan and Esposito both fall over themselves complimenting her. She just grins and tells them _I ain't afraid of no ghosts, guys_.

Castle's mildly disappointed - he's spent the past month delicately hinting at several fantastically slutty costumes he thought she might like, even to the point of leaving a catalogue on her pillow open to the page of harem girl outfits - but, well, she's Kate Beckett. She's surprising. She's an enigma. And she's hot in _anything_, because now he gets to take it all off her.

And if she's not going to show skin, he's just glad she's appealing to the geek he knows she is, deep down. Ghostbusters is a good start. He's pretty sure he can slowly warm her up to the Princess Leia bikini eventually.

She leaves before the party ends, claiming she's tired. He knows she really just wants Gates to see her leaving. Gates doesn't know about them yet. They've talked, and while Ryan and Esposito are trusted and sworn to secrecy, they're not sure about the captain. Kate's still on thin ice after her suspension and needs to keep her nose clean for a while. Castle doesn't want to get thrown out of the precinct and Having Hot Wild Sex With The Partner He's Pathetically In Love With is still list of things he's not technically supposed to be doing. So they're keeping it secret, at least for now.

After the last few guests scatter, he throws on a jacket over his costume and heads for Kate's apartment. Mother's still at the loft. She finds it amusing that he and Kate hid their relationship so long. _Honestly, darling. I've been waiting to see this for years now. You don't think it's a surprise, do you?_

The city is alive with crazies, as he figured it would be, but he calls his car service and gets to her place soon, knocking sharply at her door. She was texting him on the way over. It was dirty. The last one was just a picture.

She opens the door.

"You're late, Mr. Castle."

Black corset.

Thigh-high fishnets.

Black hat.

G-string.

Handcuffs.

Holy _shit_.

She's a slutty cop.

He stumbles inside, fumbling to shut the door behind him, trying to form words but failing. Because she's stalking towards him, shoving him back against the door. Hard.

She hisses into his ear, her voice _dripping_ with sex. "Richard Castle, you are under arrest for public indecency and lewd behavior."

"I don't remember you complaining, Detective."

That's hot enough, but then she perp-walks him to her bedroom and cuffs him to her headboard. And starts the interrogation.

He holds it together when she crawls up onto him, even when she rips off his shirt and undoes his belt. He groans as she slides her hand into the front of his pants (they're already tight and she is _not_ helping), her fingers caressing him lazily through his boxers before she pulls back. He throws his head back, trying to breathe, watching her with hazy eyes. She's not - she's not touching him, and he doesn't -

- and then he sees that her hands are sliding under her own skirt.

_Fuck_.

He's so hard he can't _move_ by the time she finishes herself off, every muscle in his body tense and straining to touch her, and honestly, he's not sure he can handle any more of this.

Then she walks out. And walks back in. With ice cubes. And starts.

Between the sharp cold of the ice and the wet heat of her mouth, his whole world narrows until the tension is unbearable and burning and it's too much and he just _surrenders_. He releases into her tight mouth with a sharp jerk of his hips, hot and dirty and blissful and oh yes yes _fuck_. Fuck.

He lies back in a daze. She wasn't kidding. She really does do magic with ice cubes.

* * *

It's late the night before his birthday when he opens his front door to find her standing there in her motorcycle leathers. Tight, black motorcycle leathers.

_Fuck_.

He doesn't really mind that his birthday present comes early. His present doesn't seem to mind either. Especially not when he starts unwrapping her.

* * *

It's strange, he has to admit. All the time it took him to finally get her naked, and he still really, really finds her clothes a turn-on.


End file.
